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1.
Purpose
To measure longitudinal (T1) and multi‐echo transverse (T2) relaxation times of healthy breast tissue at 3 Tesla (T).Materials and Methods
High‐resolution relaxation time measurements were made in six healthy female subjects. Inversion recovery images were acquired at 10 inversion times between 100 ms and 4000 ms, and multiple spin echo images were acquired at 16 echo times between 10 ms and 160 ms.Results
Longitudinal relaxation times T1 were measured as 423 ± 12 ms for adipose tissue and 1680 ± 180 ms for fibroglandular tissue. Multi‐echo transverse relaxation times T2 were measured as 154 ± 9 ms for adipose tissue and 71 ± 6 ms for fibroglandular tissue. Histograms of the voxel‐wise relaxation times and quantitative relaxation time maps are also presented.Conclusion
T1 and multi‐echo T2 relaxation times in normal human breast tissue are reported. These values are useful for pulse sequence design and optimization for 3T breast MRI. Compared with the literature, T1 values are significantly longer at 3T, suggesting that longer repetition time and inversion time values should be used for similar image contrast. J. Magn. Reson. Imaging 2010;32:982–987. © 2010 Wiley‐Liss, Inc. 相似文献2.
Adam Krasinski MSc Bernard Chiu PhD Aaron Fenster PhD Grace Parraga PhD 《Journal of magnetic resonance imaging : JMRI》2009,29(4):901-908
Purpose
To evaluate differences in carotid atherosclerosis measured using magnetic resonance imaging (MRI) and three‐dimensional ultrasound (3DUS).Materials and Methods
Ten subject volunteers underwent carotid 3DUS and MRI (multislice black blood fast spin echo, T1‐weighted contrast, double inversion recovery, 0.5 mm in‐plane resolution, 2 mm slice, 3.0 T) within 1 hour. 3DUS and MR images were manually segmented by two observers providing vessel wall and lumen contours for quantification of vessel wall volume (VWV) and generation of carotid thickness maps.Results
MRI VWV (1040 ± 210 mm3) and 3DUS VWV (540 ± 110 mm3) were significantly different (P < 0.0001). When normalized for the estimated adventitia volume, mean MRI VWV decreased 240 ± 50 mm3 and was significantly different from 3DUS VWV (P < 0.001). Two‐dimensional carotid maps showed qualitative evidence of regional differences in the plaque and vessel wall thickness between MR and 3DUS in all subjects. Power Doppler US confirmed that heterogeneity in the common carotid artery in all patients resulted from apparent flow disturbances, not atherosclerotic plaque.Conclusion
MRI and 3DUS VWV were significantly different and carotid maps showed homogeneous thickness differences and heterogeneity in specific regions of interest identified as MR flow artifacts in the common carotid artery. J. Magn. Reson. Imaging 2009;29:901–908. © 2009 Wiley‐Liss, Inc. 相似文献3.
Carl M Sanal HT Diaz E Du J Girard O Statum S Znamirowski R Chung CB 《Journal of magnetic resonance imaging : JMRI》2011,34(6):1458-1464
Purpose:
To use a tissue specific algorithm to numerically optimize UTE sequence parameters to maximize contrast within temporomandibular joint (TMJ) donor tissue.Materials and Methods:
A TMJ specimen tissue block was sectioned in a true sagittal plane and imaged at 3 Tesla (T) using UTE pulse sequences with dual echo subtraction. The MR tissue properties (PD, T2, T2*, and T1) were measured and subsequently used to calculate the optimum sequences parameters (repetition time [TR], echo time [TE], and θ).Results:
It was found that the main contrast available in the TMJ could be obtained from T2 (or T2*) contrast. With the first echo time fixed at 8 μs and using TR = 200 ms, the optimum parameters were found to be: θ ≈ 60°, and TE2 ≈ 15 ms, when the second echo is acquired using a gradient echo and θ ≈ 120°, and TE2 ≈ 15 ms, when the second echo is acquired using a spin echo.Conclusion:
Our results show that MR signal contrast can be optimized between tissues in a systematic manner. The MR contrast within the TMJ was successfully optimized with facile delineation between disc and soft tissues. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc. 相似文献4.
Heye T Yang SR Bock M Brost S Weigand K Longerich T Kauczor HU Hosch W 《European radiology》2012,22(6):1224-1232
Objectives
To evaluate hepatic relaxation times T1, T2 and T2* in healthy subjects and patients with liver cirrhosis stratified by the Child-Pugh classification (CPC).Methods
Sixty-one consecutive patients were stratified by CPC (class A?=?26; B?=?20; C?=?15) and compared with age-matched controls (n?=?31). Relaxometry measurements were performed at 1.5?T using six saturation recovery times (200–3,000?ms) to determine liver T1, six echo times (TE 14–113?ms) for T2 and eight TE (4.8–38?ms) for T2* assessment. Signal intensities in selected regions of interest in the liver parenchyma were fitted to theoretical models with least squares minimisation algorithms to determine T1, T2 and T2*.Results
The most significant difference was the higher T1 values (852?±?132?ms) in cirrhotic livers compared with controls (678?±?45?ms, P?0.0001). A less significant difference was seen for T2* (23?±?5 vs. 26?±?7?ms). Subdifferentiation showed a statistically significant difference between control group and individual CPC classes as well as between class C and classes A or B for T1 relaxation times.Conclusion
Measurement of T1 relaxation time can differentiate healthy subjects from patients with liver cirrhosis, and can distinguish between mild/moderate disease (CPC A/B) and advanced disease (CPC C).Key Points
? Significantly elevated magnetic resonance T1 relaxation times are found in liver cirrhosis. ? T1 relaxation times can distinguish healthy subjects from patients with liver cirrhosis. ? T1 relaxation times can distinguish Child–Pugh classes A and B from C. 相似文献5.
Kim KA Park MS Kim IS Kiefer B Chung WS Kim MJ Kim KW 《Journal of magnetic resonance imaging : JMRI》2012,36(2):405-410
Purpose:
To quantify liver T1 relaxation times before and after oxygen inhalation in patients with and without liver cirrhosis using a 3 Tesla (T) MRI.Materials and Methods:
Institutional Review Board approval and written informed consent were obtained. Ninety‐two noncirrhotic patients and 87 patients with hepatitis B viral liver cirrhosis (72 Child‐Pugh class A and 15 Child‐Pugh class B or C) underwent MRI with a 3.0T system before and after the supply of 100% oxygen at a rate of 15 L/min by means of a nonrebreather ventilation mask for 3 min. T1 maps were acquired using three‐dimensional spoiled gradient echo sequences with two different flip angles (2° and 14°) and a fixed TR/TE (2.54 ms/0.95 ms). Liver T1 values were obtained using a T1 processing tool (MapIT software). The mean baseline T1 values of three groups (control, Child‐Pugh class A, and Child‐Pugh class B/C) were compared using an analysis of variance test. Liver T1 value before and after oxygenation was compared using a paired t‐test for each group.Results:
The baseline liver T1 value was significantly higher in the control group (941 ± 136 ms) than in Child‐Pugh A (858 ± 143 ms) and Child‐Pugh B/C (783 ± 164 ms) group (P < 0.001 and P < 0.0001). The reduction in the liver T1 value after oxygen inhalation was significant in the control group (P = 0.012) but not significant in Child‐Pugh class A (P = 0.079) and Child‐Pugh class B/C (P = 0.752).Conclusion:
The baseline liver T1 relaxation time was significantly different between the patients with and without liver cirrhosis. The shortening effect of oxygen on the liver T1 value was significant in the control group but not in the cirrhotic patients. J. Magn. Reson. Imaging 2012;36:405–410. © 2012 Wiley Periodicals, Inc. 相似文献6.
Feiyu Li MD Vasily L. Yarnykh PhD Thomas S. Hatsukami MD Baocheng Chu MD PhD Niranjan Balu PhD Jinnan Wang PhD Hunter R. Underhill MD Xihai Zhao MD Robin Smith BS Chun Yuan PhD 《Journal of magnetic resonance imaging : JMRI》2010,31(1):168-176
Purpose:
To evaluate interscan reproducibility of both vessel morphology and tissue composition measurements of carotid atherosclerosis using a fast, optimized, 3T multicontrast protocol.Materials and Methods:
A total of 20 patients with carotid stenosis >15% identified by duplex ultrasound were recruited for two independent 3T MRI (Philips) scans within one month. A multicontrast protocol including five MR sequences was applied: TOF, T1‐/T2‐/PD‐weighted and magnetization‐prepared rapid acquisition gradient‐echo (MP‐RAGE). Carotid artery morphology (wall volume, lumen volume, total vessel volume, normalized wall index, and mean/maximum wall thickness) and plaque component size (lipid rich/necrotic core, calcification, and hemorrhage) were measured over two time points.Results:
After exclusion of images with poor image quality, 257 matched locations from 18 subjects were available for analysis. For the quantitative carotid morphology measurements, coefficient of variation (CV) ranged from 2% to 15% and intraclass correlation coefficient (ICC) ranged from 0.87 to 0.99. Except for maximum wall thickness (ICC = 0.87), all ICC were larger than 0.90. For the quantitative plaque composition measurements, the ICC of the volume and relative content of lipid rich/necrotic core and calcification were larger than 0.90 with CV ranging from 22% to 32%.Conclusion:
The results from the multicontrast high‐resolution 3T MR study show high reliability for carotid morphology and plaque component measurements. 3T MRI is a reliable tool for longitudinal clinical trials, with shorter scan time compared to 1.5T. J. Magn. Reson. Imaging 2010;31:168–176. © 2009 Wiley‐Liss, Inc. 相似文献7.
Georgeta Mihai PhD Yiu‐Cho Chung PhD Ali Merchant MD Orlando P. Simonetti PhD Sanjay Rajagopalan MD 《Journal of magnetic resonance imaging : JMRI》2010,31(2):502-509
Purpose:
To evaluate the feasibility of the dark blood fast spin echo (FSE) T1‐weighted–Sampling Perfection with Application of optimized Contrasts using different flip angle Evolution (T1w‐SPACE) sequence in assessing whole body arterial wall information from the extracranial carotids to the popliteal artery.Materials and Methods:
Twenty‐eight subjects were subjected to noncontrast, dark blood whole body magnetic resonance angiography (DB‐WBMRA) using a T1w‐SPACE sequence optimized for each of the individual stations: carotid artery, thoracic aorta, abdominal aorta, and thigh/superficial femoral artery (SFA). Image quality/vessel wall visualization and the time required to image the four stations were evaluated. Two observers checked the reproducibility of vessel wall depiction by performing quantitative measurements in registered initial and repeat studies (six subjects) of vessel wall and lumen area at 17 locations along the arterial tree.Results:
In 25 of the 28 scanned subjects, dark blood arterial images acquired in approximately 1 hour total imaging time allowed whole body arterial vessel wall visualization. Quantitative measurements showed high correlation between the initial and repeat studies for each of the observers as well as high interobserver reproducibility (r > 0.95; P < 0.01).Conclusion:
DB‐WBMRA using T1w‐SPACE is feasible and can be performed with a high degree of reliability. J. Magn. Reson. Imaging 2010; 31: 502–509. © 2010 Wiley‐Liss, Inc. 相似文献8.
Li Dong MD Jinnan Wang PhD Vasily L. Yarnykh PhD Hunter R. Underhill MD Moni B. Neradilek PhD Nayak Polissar PhD Thomas S. Hatsukami MD Chun Yuan PhD 《Journal of magnetic resonance imaging : JMRI》2010,32(2):452-458
Purpose:
To determine if better flow suppression can meaningfully improve the reproducibility of measurements associated with carotid atherosclerotic disease, particularly for lumen and wall areas.Materials and Methods:
Eighteen subjects with carotid artery stenosis identified by duplex ultrasound (11 with 16%–49% stenosis; 7 with 50%–79% stenosis) underwent two carotid magnetic resonance imaging (MRI) examinations on a 3T scanner with a 4‐channel phased array coil. High‐resolution intermediate‐weighted TSE (TR/TE = 4000/8.5 msec, 0.55 mm in‐plane resolution, 2 mm slice thickness, 16 slices, 3‐minute scan time) with two different flow‐suppression techniques (multislice double inversion recovery [mDIR] and motion‐sensitized driven‐equilibrium [MSDE]) were obtained separately. For each subject, bilateral arteries were reviewed. One radiologist blinded to timepoints, flow suppression techniques, and clinical information measured the arterial lumen area, wall area, and total vessel wall area.Results:
Compared to mDIR, the MSDE technique had a smaller interscan standard deviation (SD) in lumen (SD: 3.6 vs. 5.2 mm2, P = 0.02), wall area measurements (SD: 4.5 vs. 6.4 mm2, P = 0.02), and a trend towards smaller SD in total vessel area measurement (SD: 4.4 vs. 4.9 mm2, P = 0.07).Conclusion:
The results from this study demonstrate that vessel wall imaging could quantify atherosclerotic plaque measurements more reliably with an improved blood suppression technique. This relationship between flow‐suppression efficiency and reproducibility of plaque measurements is important, as more reliable area measurements will be useful in clinical diagnosis and in serial MRI studies that monitor carotid atherosclerotic lesion progression and regression. J. Magn. Reson. Imaging 2010;32:452–458. © 2010 Wiley‐Liss, Inc. 相似文献9.
Thomas Henzler MD Olaf Dietrich PhD Radko Krissak MD Tobias Wichmann MSc Titus Lanz PhD Maximilian F. Reiser MD Stefan O. Schoenberg MD Christian Fink MD 《Journal of magnetic resonance imaging : JMRI》2009,30(3):541-546
Purpose
To assess the feasibility of half‐Fourier‐acquisition single‐shot turbo spin‐echo (HASTE) of the lung at 3 Tesla (T) using parallel imaging with a prototype of a 32‐channel torso array coil, and to determine the optimum acceleration factor for the delineation of intrapulmonary anatomy.Materials and Methods
Nine volunteers were examined on a 32‐channel 3T MRI system using a prototype 32‐channel‐torso‐array‐coil. HASTE‐MRI of the lung was acquired at both, end‐inspiratory and end‐expiratory breathhold with parallel imaging (Generalized autocalibrating partially parallel acquisitions = GRAPPA) using acceleration factors ranging between R = 1 (TE = 42 ms) and R = 6 (TE = 16 ms). The image quality of intrapulmonary anatomy and subjectively perceived noise level was analyzed by two radiologists in consensus. In addition quantitative measurements of the signal‐to‐noise ratio (SNR) of HASTE with different acceleration factors were assessed in phantom measurements.Results
Using an acceleration factor of R = 4 image blurring was substantially reduced compared with lower acceleration factors resulting in sharp delineation of intrapulmonary structures in expiratory scans. For inspiratory scans an acceleration factor of 2 provided the best image quality. Expiratory scans had a higher subjectively perceived SNR than inspiratory scans.Conclusion
Using optimized multi‐element coil geometry HASTE‐MRI of the lung is feasible at 3T with acceleration factors up to 4. Compared with nonaccelerated acquisitions, shorter echo times and reduced image blurring are achieved. Expiratory scanning may be favorable to compensate for susceptibility associated signal loss at 3T. J. Magn. Reson. Imaging 2009;30:541–546. © 2009 Wiley‐Liss, Inc. 相似文献10.
van 't Klooster R de Koning PJ Dehnavi RA Tamsma JT de Roos A Reiber JH van der Geest RJ 《Journal of magnetic resonance imaging : JMRI》2012,35(1):156-165
Purpose:
To develop and validate an automated segmentation technique for the detection of the lumen and outer wall boundaries in MR vessel wall studies of the common carotid artery.Materials and Methods:
A new segmentation method was developed using a three‐dimensional (3D) deformable vessel model requiring only one single user interaction by combining 3D MR angiography (MRA) and 2D vessel wall images. This vessel model is a 3D cylindrical Non‐Uniform Rational B‐Spline (NURBS) surface which can be deformed to fit the underlying image data. Image data of 45 subjects was used to validate the method by comparing manual and automatic segmentations. Vessel wall thickness and volume measurements obtained by both methods were compared.Results:
Substantial agreement was observed between manual and automatic segmentation; over 85% of the vessel wall contours were segmented successfully. The interclass correlation was 0.690 for the vessel wall thickness and 0.793 for the vessel wall volume. Compared with manual image analysis, the automated method demonstrated improved interobserver agreement and inter‐scan reproducibility. Additionally, the proposed automated image analysis approach was substantially faster.Conclusion:
This new automated method can reduce analysis time and enhance reproducibility of the quantification of vessel wall dimensions in clinical studies. J. Magn. Reson. Imaging 2012;35:156‐165. © 2011 Wiley Periodicals, Inc. 相似文献11.
Biasiolli L Lindsay AC Choudhury RP Robson MD 《Journal of magnetic resonance imaging : JMRI》2011,33(5):1136-1143
Purpose:
To test whether the k‐space acquisition strategy used by fast‐spin‐echo (FSE) is a major source of blurring in carotid wall and plaque imaging, and investigate an alternative acquisition approach.Materials and Methods:
The effect of echo train length (ETL) and T2 on the amount of blurring was studied in FSE simulations of vessel images. Edge sharpness was measured in black‐blood T1 and proton‐density weighted (T1W and PDW) carotid images acquired from 5 normal volunteers and 19 asymptomatic patients using both FSE and multiple‐spin‐echo (Multi‐SE) sequences at 3 Tesla. Plaque images were classified and divided in group α (tissues' average T2 ~40–70 ms) and group β (plaque components with shorter T2).Results:
Simulations predicted 26.9% reduction of vessel edge sharpness from Multi‐SE to FSE images (ETL = 9, T2 = 60 ms). This agreed with in vivo measurements in normal volunteers (27.4%) and in patient group α (26.2%), while in group β the loss was higher (31.6%).Conclusion:
FSE significantly reduced vessel edge sharpness along the phase‐encoding direction in T1W and PDW images. Blurring was stronger in the presence of plaque components with short T2 times. This study shows a limitation of FSE and the potential of Multi‐SE to improve the quality of carotid imaging. J. Magn. Reson. Imaging 2011;33:1136–1143. © 2011 Wiley‐Liss, Inc. 相似文献12.
Sijens PE Oudkerk M Reijngoud DJ Leenders KL de Valk HW van Spronsen FJ 《European radiology》2004,14(10):1895-1900
Short echo time single voxel methods were used in previous MR spectroscopy studies of phenylalanine (Phe) levels in phenylketonuria (PKU) patients. In this study, apparent T
2 relaxation time of the 7.3-ppm Phe multiplet signal in the brain of PKU patients was assessed in order to establish which echo time would be optimal. 1H chemical shift imaging (CSI) examinations of a transverse plain above the ventricles of the brain were performed in 10 PKU patients and 11 persons not suffering from PKU at 1.5 T, using four echo times (TE 20, 40, 135 and 270 ms). Phe was detectable only when the signals from all CSI voxels were summarized. In patients suffering from PKU the T
2 relaxation times of choline, creatine and N-acetyl aspartate (NAA) were similar to those previously reported for healthy volunteers (between 200 and 325 ms). The T
2 of Phe in brain tissue was 215±120 ms (standard deviation). In the PKU patients the brain tissue Phe concentrations were 141±69 M as opposed to 58±23 M in the persons not suffering from PKU. In the detection of Phe, MR spectroscopy performed at TE 135 or 270 ms is not inferior to that performed at TE 20 or 40 ms (all previous studies). Best results were obtained at TE=135 ms, relating to the fact that at that particular TE, the visibility of a compound with a T
2 of 215 ms still is good, while interfering signals from short-TE compounds are negligible. 相似文献
13.
Nicolaas A.J. Puts PhD Peter B. Barker DPhil Richard A.E. Edden PhD 《Journal of magnetic resonance imaging : JMRI》2013,37(4):999-1003
Purpose:
To measure the in vivo longitudinal relaxation time T1 of GABA at 3 Tesla (T).Materials and Methods:
J‐difference edited single‐voxel MR spectroscopy was used to isolate γ‐aminobutyric acid (GABA) signals. An increased echo time (80 ms) acquisition was used, accommodating the longer, more selective editing pulses required for symmetric editing‐based suppression of co‐edited macromolecular signal. Acquiring edited GABA measurements at a range of relaxation times in 10 healthy participants, a saturation‐recovery equation was used to model the integrated data.Results:
The longitudinal relaxation time of GABA was measured as T1,GABA = 1.31 ± 0.16 s.Conclusion:
The method described has been successfully applied to measure the T1 of GABA in vivo at 3T. J. Magn. Reson. Imaging 2013;37:999–1003. © 2012 Wiley Periodicals, Inc. 相似文献14.
Dimitris Mitsouras Christopher D. Owens Michael S. Conte Hale Ersoy Mark A. Creager Frank J. Rybicki Robert V. Mulkern 《Magnetic resonance in medicine》2009,62(3):607-615
Lower extremity peripheral vein bypass grafts (LE‐PVBG) imaged with high‐resolution black blood three‐dimensional (3D) inner‐volume (IV) fast spin echo (FSE) MRI at 1.5 Tesla possess a two‐layer appearance in T1W images while only the inner layer appears visible in the corresponding T2W images. This study quantifies this difference in six patients imaged 6 months after implantation, and attributes the difference to the T2 relaxation rates of vessel wall tissues measured ex vivo in two specimens with histologic correlation. The visual observation of two LE‐PVBG vessel wall components imaged in vivo is confirmed to be significant (P < 0.0001), with a mean vessel wall area difference of 6.8 ± 2.7 mm2 between contrasts, and a ratio of T1W to T2W vessel wall area of 1.67 ± 0.28. The difference is attributed to a significantly (P < 0.0001) shorter T2 relaxation in the adventitia (T2 = 52.6 ± 3.5 ms) compared with the neointima/media (T2 = 174.7 ± 12.1 ms). Notably, adventitial tissue exhibits biexponential T2 signal decay (P < 0.0001 vs monoexponential). Our results suggest that high‐resolution black blood 3D IV‐FSE can be useful for studying the biology of bypass graft wall maturation and pathophysiology in vivo, by enabling independent visualization of the relative remodeling of the neointima/media and adventitia. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
15.
Hiroyuki Fujimori Thomas Michaelis Markus Wick Jens Frahm 《Magnetic resonance in medicine》1998,39(4):647-650
Putative changes of metabolite T2 relaxation times were investigated before and after a 20-min period of global ischemia in rat brain in vivo (n= 10) using localized proton MRS at different echo times (2.35 T). Neither absolute T2 relaxation times (TE = 20-270 ms) nor time courses of T2-weighted metabolite signals (TE = 135 ms) revealed statistically significant changes during the occlusion or early reperfusion relative to pre-ischemic baseline. These findings are in line with reports of relaxation changes at much later stages and further demonstrate that altered T2 relaxation is not a confounding factor in diffusion-weighted long-TE proton MRS during early ischemic events. 相似文献
16.
John D. Port MD PhD Karen E. Rampton MD Yunhong Shu PhD Armando Manduca PhD Mark A. Frye MD 《Journal of magnetic resonance imaging : JMRI》2013,37(6):1451-1459
Purpose:
(i) To develop an MRS technique to measure 7Li levels in human brain in a reasonable scan time, (ii) to develop a technique to quantify 7Li T2 relaxation times as measured from human brain in patients taking lithium for the treatment of their bipolar disorder, and (iii) to confirm or refute the presence of bi‐exponential 7Li T2 relaxation in human brain.Materials and Methods:
We modified a spin‐echo MRS pulse sequence to decrease its minimum echo time. With IRB approval, we performed lithium MRS with the modified pulse sequence on 13 euthymic bipolar patients stable on long‐term lithium to treat their disease.Results:
We were able to achieve a total scan time per sample of 8:20; total scan time including imaging, calibration and MRS was approximately 1 h 15 min. We observed bi‐exponential T2 relaxation in the majority of patients, with an average short decay time of 5.3 ± 1.4 ms and an average long decay time of 68.2 ± 10.2 ms. However, in two patients we observed strongly mono‐exponential T2 relaxation with an average decay time of 47.4 ± 1.3 ms.Conclusion:
7Li relaxation patterns may prove useful to distinguish between lithium‐responsive and lithium nonresponsive bipolar patients. J. Magn. Reson. Imaging 2013;37:1451–1459. © 2012 Wiley Periodicals, Inc. 相似文献17.
Yamashita K Yoshiura T Hiwatashi A Kamano H Honda H 《Dento maxillo facial radiology》2012,41(7):601-604
Objective
The aim of this study was to assess the feasibility of ultrashort echo time (UTE) imaging in the visualization of middle ear ossicles in normal subjects.Methods
12 young adult volunteers (males/females = 6/6, age 25–44 years, mean 30.3 years) with normal hearing levels underwent MRI studies using a 3.0 T clinical unit with an eight-channel SENSE head coil. For each subject, the whole head was imaged using a three-dimensional dual-echo UTE imaging sequence with radial trajectory and the following parameters: field of view, 240 × 240 × 240 mm; matrix, 320 × 320; flip angle, 7°; repetition time/echo time (TE)1/TE2, 8.0 ms/0.14 ms/1.8 ms; acquisition voxel size, 0.75 × 0.75 × 0.75 mm; number of signals averaged, 1; imaging time, 27 min 20 s. Subsequently, subtraction images were obtained by subtracting long TE (1.8 ms) images from short TE (0.14 ms) images. By using these three images, the visibility of the bilateral middle ear ossicles was evaluated. Moreover, as a reference for the UTE findings, CT images of the temporal bone were obtained in one volunteer.Results
In all subjects, the middle ear ossicles were clearly visualized as a high signal intensity spot surrounded by a signal void of air on short TE images bilaterally, while they were not visible in long TE images in any of the subjects. The subtraction images provided better contrast of the ossicles.Conclusion
We demonstrated the feasibility of UTE imaging of the middle ear ossicle in normal subjects. 相似文献18.
Purpose
To assess the feasibility of black‐blood turbo spin‐echo imaging of the left anterior descending coronary artery wall at 3 Tesla under free‐breathing and breath‐hold conditions.Materials and Methods
Proton density‐weighted black‐blood turbo spin‐echo imaging of the left anterior descending coronary artery was performed on 15 volunteers on a 3 T whole body scanner with an eight channel phased array coil. Volunteers were imaged during free‐breathing (with navigators, N = 5), or with breath‐hold (N = 5), or both (N = 2). Imaging was not possible in three volunteers due to either gradient or radiofrequency (RF) coupling with the electrocardiogram (ECG). Images were analyzed to determine coronary artery wall thickness, wall area, lumen diameter, and lumen area. Signal‐to‐noise and contrast‐to‐noise ratios were calculated.Results
Coronary artery wall thickness, wall area, lumen diameter, and lumen area measurements were consistent with previous magnetic resonance (MR) measurements of the coronary wall at 1.5 Tesla.Conclusion
Coronary wall imaging using free‐breathing and breath‐hold two‐dimensional black‐blood TSE is feasible at 3 T. Further improvement in resolution and image quality is required to detect and characterize coronary plaque. J. Magn. Reson. Imaging 2005;21:128–132. © 2005 Wiley‐Liss, Inc.19.
Partridge SC Vanantwerp RK Doot RK Chai X Kurland BF Eby PR Specht JM Dunnwald LK Schubert EK Lehman CD Mankoff DA 《Journal of magnetic resonance imaging : JMRI》2010,32(5):1124-1131
Purpose:
To investigate the contrast of three‐dimensional balanced steady state free precession (3D bSSFP) in the two component T2 model and to apply the results to optimize 3D bSSFP for prostate imaging at 1.5 Tesla.Materials and Methods:
In each of seven healthy volunteers, six 3D bSSFP acquisitions were performed with flip angles (α) equally spaced between 10° and 110°. Predictions of signal and contrast were obtained from synthetic bSSFP images calculated from relaxation parameters obtained from a multi‐spin‐echo acquisition. One biexponential and two monoexponential models were applied. Measured and predicted signals were compared by simple linear regression.Results:
The measured contrast to signal ratio increased continuously with α. Mean R2 for the biexponential model was almost constant for α in the range 50–110°. The biexponential model was a better predictor of the measured signal than the monoexponential model. A monoexponential model restricted to the echoes TE = 50–125 ms performed similar to the biexponential model. The predicted contrast peaked at α between 50° and 90°.Conclusion:
Prostate imaging with bSSFP benefited from high flip angles. The biexponential model provided good signal prediction while predictions from the monoexponential models are dependent on the range of TE used for T2 determination. J. Magn. Reson. Imaging 2010;31:1124–1131. © 2010 Wiley‐Liss, Inc. 相似文献20.
Hodgson RJ Menon N Grainger AJ O'Connor PJ McGonagle D Helliwell P Emery P Robson MD 《The British journal of radiology》2012,85(1015):e293-e299